This dark chocolate mousse cake has ultra moist chocolate cake layers and an easy chocolate mousse made without eggs. The whole thing is covered in dark chocolate ganache, making it the perfect cake for chocolate lovers.
Why You’ll Love This Recipe
This dark chocolate mousse cake is a dream for chocolate lovers. Imagine making a chocolate cake, but instead of frosting, a thick layer of fluffy chocolate mousse sits between each layer.
- The chocolate cake layers are super soft and moist, made with dark cocoa powder for a deep color and flavor. As a bonus is it possible to make the entire cake batter in just one bowl.
- There is chocolate mousse sandwiched between each layer of cake. The mousse is simple to make and doesn’t require any gelatin or eggs.
- Using dark chocolate across all parts of the recipe ensures a rich flavor that is not too sweet, despite its indulgent appearance.
- It is possible to prepare cake layers and chocolate mousse in advance to simplify your life.
- A perfect cake for nice events or Valentine’s Day.
If you love dark chocolate cake, I also recommend checking out these dark chocolate cupcakes or dark chocolate hazelnut cupcakes.
Key Ingredients Needed
Here are some of the key ingredients needed to make chocolate mousse cake as well as important notes. You can find a full list of ingredients on the recipe card at the bottom of this post.
Dark Chocolate Cake
- Dark Cocoa Powder: Hershey’s Special Dark and the King Arthur Dark Blend are both great options that I have had success with. If you don’t have dark cocoa, use dutch-processed cocoa. Skip the natural cocoa powder this time around (usually labeled unsweetened or undutched cocoa), which is more acidic and lighter in color.
- Boiling Water: Use boiling water to bloom the cocoa powder. More on this later.
- Oil: Oil serves as the primary fat source for the dark chocolate cake. I prefer oil over butter when it comes to chocolate cake since it makes it moister and fluffier.
- Eggs, warmed to room temperature: Soak eggs in a bowl of hot water for 5-10 minutes to bring them to room temperature.
- Buttermilk: Buttermilk makes this chocolate cake really moist and delicious! If you don’t have buttermilk I have had success using equal parts milk and Greek yogurt or sour cream.
- Granulated Sugar and Light Brown Sugar: Using some light brown sugar in addition to granulated sugar adds a hint of molasses for extra richness.
Chocolate Mousse
- Dark Cocoa Powder: Similar to the chocolate cake, use a dark or dutch-processed cocoa powder for the best results.
- Chopped Dark or Bittersweet Chocolate: Aim for around a 60% cocoa, any darker than 70% will be too bitter and there isn’t much added sugar in the mousse. I love the Ghiradelli Bittersweet Baking Bars.
- Whole Milk: Use milk to dissolve the cocoa powder and melt with chopped chocolate. Whole milk delivers the best flavor, but you can substitute skim milk if desired.
- Heavy Whipping Cream: Lots of heavy whipping cream make up the base of the chocolate mousse.
- Pure Vanilla Extract: Vanilla actually helps bring out the chocolate flavor, which I know if funny because they’re often considered opposing flavors.
Tips for The Best Chocolate Cake
- Do not reduce the amount of sugar in the cake. Sugar is actually crucial to a moist chocolate cake. There is a ton of liquid in this cake between the boiling water and the buttermilk. Sugar is hydrophilic and therefore absorbs water molecules, preventing them from evaporating during baking.
- Use light colored, uncoated metal cake pans. The pan you use can make a huge difference in the final outcome. The reason why light pans are better than dark, is that dark pans absorb and distribute heat much more quickly. This means the cake could become burnt and charred around the edges before the middles are done.
- Fat Daddios and USA Pan both make really great cake pans.
- Room temperature ingredients. Make sure that the eggs and buttermilk are warmed as close to room temperature as possible before baking. Since cold ingredients do not mix together as well, using room temperature ingredients results in a more even batter and better-textured chocolate cake.
Tips for Chocolate Mousse
This chocolate mousse without eggs or gelatin is simple and easy to make. Once you’ve mastered it you may just find yourself whipping up chocolate mousse whenever you please (yes you can just eat this mousse as-is hehe). However, there are a few things you will want to keep in mind — particularly temperature and gentleness.
- Keep the heavy cream cold. The key to heavy cream that whips up successfully is not being afraid of a little cold. Room temperature heavy cream just won’t whip up properly. Keep the heavy cream in the refrigerator until you are ready to use it and feel free to freeze the whisk before using.
- Ensure melted chocolate is cool before folding into cream. Remember that thing about temperature? It’s important not just for the heavy cream. Part of the recipe involves folding melted chocolate with whipped cream together. If the chocolate is warm, as you can imagine the whipped cream will melt. To prevent this, make sure that the chocolate is cool but still melted.
- Be gentle when folding. When folding together whipped cream and chocolate, it’s important to be flow and gentle so as to not deflate the cream too much and turn it into a runny mess. I like to use a flexible rubber spatula and swirl it around the edges, folding the cream and chocolate together.
Frequently Asked Questions
How should I store leftover chocolate mousse cake?
Store leftover cake tightly wrapped in the refrigerator, which is is best enjoyed within 3-4 days. Do not keep the cake out on the counter, as the mousse will melt.
Why didn’t my CHOCOLATE cake rise?
This cake isn’t designed to rise super tall with big domes. That being said, if your cake is sunken in the middle there are a few things you can troubleshoot. First, make sure that your leavening agents are fresh as they lose potency over next. Next, make sure that you maintain a consistent oven temperature and to not open the door until the cake is done. Lastly, bake the batter as soon as possible after you make it, as the leavening agents will get to work as soon as they come into contact with liquid. The longer you wait, the flatter the cake.
Why do you use boiling water?
Adding boiling water to cocoa powder ‘blooms’ it. Essentially what you are doing is dissolving the cocoa solids in a hot liquid, which releases all those lovely chocolate flavors inside. This results in a richer, more intense chocolate flavor.
How many cake pans should I use?
I used two deep 8″ round cake pans, and then cut each cake in half hamburger-style to create four layers. You could alternatively bake this cake in four 8″ pans, but will need to reduce the baking time down to 19-24 minutes to compensate for the thinner layers.
Pin and Save for Later
Not ready to bake yet but want to come back to this recipe? No problem! Simply hover over any image in this post (or tap on mobile) to save this recipe to your favorite baking Pinterest board.
Happy baking and hope you love your dark chocolate mousse cake! <3
Dark Chocolate Mousse Cake
Rich and moist dark chocolate cake layered with an easy-to-make chocolate mousse and topped with dark chocolate ganache. This cake is a perfect indulgent dessert for all of the chocolate lovers out there!
Ingredients
Chocolate Mousse
- ½ cup hot milk
- 2 tbsp (10Gg) unsweetened cocoa powder
- 8 oz (215g) good quality dark chocolate bars, finely chopped
- 1 tsp pure vanilla extract or vanilla bean paste
- Pinch of salt
- 1½ cups heavy whipping cream
- 2 Tablespoons (15g) powdered (confectioners) sugar
Chocolate Cake
- ¾ cup (60g) dark cocoa powder (such as Hershey's Special Dark)
- ¾ cup boiling water
- ½ cup vegetable oil
- 1 ½ cups (300g) granulated sugar
- ¼ cup (50g) light brown sugar
- 2 large eggs, room temperature
- ¾ cup buttermilk, room temperature
- 2 tsp vanilla extract
- 1 ¾ cups (210g) all-purpose flour
- 1 tsp baking powder
- 1 tsp baking soda
- ½ tsp salt
Chocolate Ganache
- 1 cup chopped dark chocolate
- ½ cup heavy cream
- pinch of salt
Instructions
Make chocolate mousse
- Place the chopped chocolate in a medium, heatproof bowl. Whisk the 2 tbsp of cocoa powder into the hot milk to dissolve, and then pour the milk over the chopped chocolate. Let rest for 1 minute, and then stir until the chocolate is fully melted and smooth. If needed, you can microwave the chocolate for 10-20 seconds to finish melting it.
- Stir in the vanilla and salt, and then let the chocolate cool down until it is still melted but no longer warm.
- Using a hand or stand mixer, beat the whipping cream and powdered sugar together until stiff peaks form to make a whipped cream. Take a large dollop of whipped cream and gently fold it into the melted chocolate. Then, transfer all of the chocolate into the bowl of whipped cream. Use a spatula to gently fold the chocolate into the cream, trying to avoid deflating or thinning out the cream.
- Cover and chill the mousse for at least 2 hours or overnight in the refrigerator.
Make the Cake
- Preheat the oven to 350°F. Grease two deep 8-inch round cake pans and line them with parchment cake liners. See notes for using more than two pans.
- Place the cocoa powder in a large, heatproof bowl. Pour the boiling water over the cocoa and whisk until it is dissolved.
- Add the oil, granulated sugar, and brown sugar, and whisk until combined. Then, add the eggs and vanilla extract and continue whisking for 30-60 seconds until the mixture is glossy and smooth. Next, whisk in the buttermilk unti combined.
- In a separate bowl, mix together the flour, baking soda, baking powder, and salt. Fold this flour mixture into the batter until there are no streaks of white remaining. Avoid over mixing.
- Divide the batter evenly between the cake pans. Use a food scale or measuring cups to help distribute. Give each cake pan a tap on the counter to release any air bubbles.
- Bake the cakes for 30-35 minutes, or until a toothpick comes out clean. Place the pans on a wire rack and allow the cakes to cool down completely before assembling.
Assemble the Cake
- Slice each cake layer in half, hamburger-style to make four layers. Skip if you baked the layers in 4 individual pans. Place one layer of cake on a board or plate and spread ⅓ of the chocolate mousse on top. Repeat with the next layer, and then repeat again.
- Place the final layer of cake on top. Overall you will have four layers of cake and three layers of mousse. From here, make the chocolate ganache that will go on the tops and sides of the cake.
Chocolate Ganache
- Place the chopped chocolate in a heatproof bowl. Heat the heavy cream until it is hot and simmering and pour it over the chocolate. Let the chocolate rest for 2 minutes to soften, and then using a spatula to stir it until it's melted and smooth. If there are still a few chunks of chocolate that aren't melting, you can pop the bowl in the microwave for 10-15 seconds, but avoid overheating it. Once the chocolate is smooth, stir in the salt.
- Let the ganache cool until it's still melted but no longer hot. Spread it over the tops and sides of the cake and then allow it to set completely.
- Chill the cake for 1-2 hours before serving and enjoy!
Notes
Cocoa Powder: Hershey's 'Special Dark' cocoa powder is my go-to for this recipe. I have also tried King Arthur's Special Dark blend and find that it also works pretty well.
Cake Pans: I chose to use two deep 8" round cake pans, and then slicing each cake into two layers once they cool. You can alternatively bake with three or four 8" pans. If doing so, reduce the bake time to around 19-23 minutes for four pans, and 24-28 minutes for three pans. Check in often though, as every oven is different. In addition, make sure to use light colored metal cake pans for the most even bake.
Timing: I recommend preparing the mousse a day in advance to save yourself time on the day you plan to serve the cake. You can also prepare the cake layers a day in advance and store them in the fridge. Make sure to leave enough time as well to chill the cake before serving!
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